Timeslot scheduling in digital audio and hybrid audio radio systems

ABSTRACT

Systems and methods of decoding data streams and conserving power are described. In some embodiments, a stream of data containing audio and other data is divided into a plurality of timeslots. A first timeslot of the plurality of timeslots is allocated to a first service. A grant allocation message which indicates a location of the first timeslot allocated to the first service is generated. The grant allocation message and the plurality of timeslots are transmitted to a receiver. The transmission system and receiver may be compatible with NRSC-5. The receiver may receive and decode the grant allocation message to identify OFDM symbols that carry information regarding the first service. The receiver may also receive the plurality of timeslots. The receiver may set a power mode of a component during OFDM symbols that indicate a status of the first service.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of prior U.S. patent application Ser.No. 12/154,882, filed May 27, 2008, entitled “Timeslot Scheduling inDigital Audio and Hybrid Audio Radio Systems,” and issued as U.S. Pat.No. ______. This application claims the benefit of U.S. ProvisionalApplication No. 60/931,703, filed May 25, 2007, and entitled “System andMethod for Adding Timeslot Scheduling and Notifications to a NRSC-5transmission system,” which is incorporated herein by reference in itsentirety. This application is related to U.S. Provisional ApplicationNo. 60/931,741, filed May 25, 2007, and entitled “NRSC-5 Radio ReceiverApparatus with Power Control,” which is incorporated herein by referencein its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate generally to radio systemsand, more particularly, to digital audio and hybrid radio systems.

2. Background Art

National Radio Standards Committee-5 (NRSC-5) and National RadioStandards Committee-5A (NRSC-5A) are standards for hybrid digital (HD™)radio which is becoming increasingly ubiquitous. NRSC-5 and NRSC-5Acompatible receivers may be deployed in a variety of products such ascar radios, portable radios, MP3 players, cell phones, and navigationdevices. For many of these products it is highly desirable for thereceiver to consume as little power as possible in order to conserve thepower life of a device battery.

SUMMARY OF THE INVENTION

Systems and methods of decoding data streams (e.g., timeslot scheduling)and power conservation are described. In some embodiments, a stream ofdata containing audio and other data is divided into a plurality oftimeslots. A first timeslot of the plurality of timeslots is allocatedto a first service. A grant allocation message which indicates alocation of the first timeslot allocated to the first service isgenerated. The grant allocation message and the plurality of timeslotsare transmitted to a receiver.

The receiver may receive and decode the grant allocation message toidentify orthogonal frequency division multiplexing (OFDM) symbols thatcarry information regarding the first service. The receiver may alsoreceive the plurality of timeslots. The receiver may set a power mode ofa component during OFDM symbols that indicate a status of the firstservice.

An exemplary system comprises a transmission system and a transmitter.The transmission system may be configured to divide a stream of datainto a plurality of timeslots, to allocate a first timeslot of theplurality of timeslots to a first service, and to generate a grantallocation message that indicates a location of the first timeslotallocated to the first service. The transmitter may be configured totransmit the grant allocation message and the plurality of timeslots toa receiver.

An exemplary system may also comprise a tuner and digital signalprocessing hardware. The tuner may be configured to receive a grantallocation message and a plurality of timeslots. The digital signalprocessing hardware may be configured to decode the grant allocationmessage to identify OFDM symbols that carry information regarding afirst service and set a power mode of a component of the tuner duringOFDM symbols that indicate a status of the first service.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an overview of a transmission system inan exemplary embodiment.

FIG. 2 is a block diagram of an exemplary scheduler in an exemplaryembodiment.

FIG. 3 depicts a sequence of grant scheduling events on a timeline in anexemplary embodiment.

FIG. 4 is a flowchart regarding transmitting a grant allocation messagein an exemplary embodiment.

FIG. 5 depicts the current NRSC-5A transmission standard provision forscheduling multiple audio services in a single P1 logical channel in theprior art.

FIG. 6 shows improved scheduling in accordance with an exemplaryembodiment.

FIG. 7 is a block diagram of L1 transmission frames wherein two audioprograms are transmitted in subsequent L1 transmission frames in anexemplary embodiment.

FIG. 8 is another block diagram of L1 transmission frames wherein twoaudio programs are transmitted in subsequent L1 transmission frames inan exemplary embodiment.

FIG. 9 is a block diagram of multiple logical channels in an exemplaryembodiment.

FIG. 10 is another block diagram of multiple logical channels in anexemplary embodiment.

FIG. 11 is a block diagram of a radio receiver in an exemplaryembodiment.

FIG. 12 is a block diagram of an exemplary tuner with a directconversion architecture in an exemplary embodiment.

FIG. 13 shows mapping grants into active symbols in an FM logicalchannel that is interleaved using interleaver I with latency of M OFDMsymbols in an exemplary embodiment.

FIG. 14 shows mapping grants into active symbols in an FM logicalchannel that is interleaved using interleaver IV with latency of K OFDMsymbols in an exemplary embodiment.

FIG. 15 shows a received transmission partitioned into a sequence ofOFDM symbols in L1 transmission frames in an exemplary embodiment.

FIG. 16 is a flowchart regarding receiving the grant allocation messagein an exemplary embodiment.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The audio system described herein may be an audio system that performsbased on an NRCS-5 standard. The NRCS-5 standard describes a digitalradio frequency broadcast system that may deliver digital audio and dataservices to radio receivers from terrestrial transmitters on existingFrequency Modulation (FM) and Amplitude Modulation (AM) radio. Thesystem identified in NRSC-5, NRSC-5A, and other Ibiquity standarddocuments uses an in-band over channel (IBOC) OFDM technology to carrydigital data streams over AM and FM bands. This system allows for acoexistence of digital modulated signals alongside a legacy analog FMand AM transmission. This system can also provide several services in asingle frequency band, such as multiple audio streams and data services.

A compatible radio receiver is constantly active. However, thecompatible radio receiver may consume less power by switching off (e.g.,deactivating) or otherwise reducing power to components unrelated toactive services. The current transmission system, however, does notprovide a method to allocate different services in a logical channel todifferent times of data transmission (i.e., timeslots). As a result, aradio receiver may need to receive and decode an entire stream of bitsbelonging to a logical channel in order to extract information neededfor any service in use.

In various embodiments, an extended transmission system allocatesdifferent services in the logical channel to different timeslots.Information regarding this allocation may be sent to a receiver therebygiving the receiver time to reduce or eliminate power to one or morecomponents of the tuner (or any other components) related to inactiveservices. Further, based on the information regarding allocation, thecompatible receiver may activate or “wake up” inactive components, orthose components in standby mode, prior to their use in newly activeservices. Those skilled in the art will appreciate that existingreceivers may need to be reconfigured or updated in order to receive andprocess the information regarding the allocation.

FIG. 1 is a diagram illustrating an overview of a transmission system102 in an exemplary embodiment. The transmission system 102 transmitsdata over the radio transmitter 104 to the radio receiver 106. Theexemplary transmission system 102 can be partitioned into threesubsystems including an audio and data input subsystem 108, a transportand service multiplex subsystem 110, a radio frequency (RF)/transmissionsubsystem 112, and a scheduler 114.

The exemplary audio and data input subsystem 108 provides for theencapsulation of audio streams and data streams into packets that can besent over the transmission system 102. The audio streams in thetransmission system 102 include a primary audio stream as well as one ormore secondary audio streams. In some cases, a source (e.g.,broadcaster) for the primary audio stream may transmit a duplication ofthe primary audio stream over a purely analog signal. It is notuncommon, however, for the source of one or more of the secondary audiostreams to include audio content not available in an analog broadcastsignal. The audio and data input subsystem 108 may compress the digitalaudio source streams within an audio transport layer and send thecompressed digital audio source streams to a transport multiplex (e.g.,the transport and service multiplex subsystem 110).

The digital data within the audio stream may comprise several differentstream types, including program service data (PSD), station informationservice (SIS) data, and advanced data services (ADS). PSD can provideinformation on an audio program that may be heard by a radio listener.For example, PSD may include a song title, an artist name, albuminformation, a genre, a comment, a commercial, and/or referenceidentifiers.

SIS data provides general information about a station's program as wellas some technical information. For example, SIS data may include astation identification number, station call letters, a station name, astation location, a station time, and/or a text message.

ADS may include broadcast data services that carry content that can beexpressed as a data file or a data stream, including audio services. Forexample, such services may include presentations of stock, news,weather, real time traffic, and entertainment programming includingaudio, text, and images.

The transmission system 102 transmits one or more logical channelstreams. Each logic channel stream may include one or more audio or dataservices. The exemplary transport and service multiplex subsystem 110takes multiple audio and data input streams and organizes these streamsinto packets. A service multiplex arranges the packets from one or moreservices into a logical channel stream.

The RF/transmission subsystem 112 receives the logical channel streamsfrom the transport and service multiplex subsystem 110 and performschannel coding and waveform generation. The RF/transmission subsystem112 may transmit a signal of the processed streams at a radio frequencyover the radio transmitter 104. Each logical channel stream may beindependently coded using a convolutional encoder, then interleaved andmodulated using orthogonal frequency division multiplexing (OFDM).Further, each logical stream may be assigned with a group of tones thatcarries the information within the stream. Those skilled in the art willappreciate that the RF/Transmission subsystem 112 may use OFDM as wellas coded orthogonal frequency division multiplexing (COFDM).

The scheduler 114 divides a continuous data transmission into a sequenceof timeslots. In one example, the scheduler 114 divides data receivedfrom the transport and service multiplex subsystem 110 and provides thetimeslots to the RF/transmission subsystem 112. In other embodiments,the scheduler 114 divides data received from the RF/transmissionsubsystem 112 and provides the timeslots to RF/transmission subsystem112 for transmission.

The scheduler 114 may allocate timeslots or portions of timeslots todifferent services carried over a single physical channel ahead of thetime of the actual transmission. The scheduler 114 may then sendbandwidth allocation messages informing receivers (e.g., radio receiver106) about allocation of services into timeslots. In some embodiments,the scheduler 114 may implement a bandwidth allocation algorithm thatattempts to create large gaps between timeslots that are allocated todata from the same service. The scheduler 114 is further described inFIG. 2.

The radio receiver 106 (e.g., an HDradio™ receiver) may receive thesignal from the radio transmitter 104 and then down-convert the signalfrom a radio frequency to an intermediate frequency. The down-convertedsignal may then be sampled and digitally demodulated to produce a streamof bits belonging to one or more logical channels. The radio receiver106 may then de-multiplex the logical channel bits to extract bitsbelonging to the service that a radio receiver 106 is currentlyproviding to a user.

In a typical usage model, the user of the radio receiver 106 will onlyuse a single service out of several services that a channel may provide.Various components (e.g., circuits or combinations of circuits) withinthe radio receiver 106 may be required to implement various services.However, if the service is not in use, one or more components may bedeactivated (i.e., set to power down mode) or placed in power standbymode where power to those unused components is reduced or completelyeliminated.

Although only one radio receiver 106 is depicted in FIG. 1, thoseskilled in the art will appreciate that any number of radio receivers106 may receive transmissions from the radio transmitter 104. Similarly,any number of radio transmitters 104 including radio transmitters 104that are not in direct communication with a transmission system (e.g.,transmission system 102) may transmit to one or more radio receivers106. Further, although only one transmission system 102 and only oneradio transmitter are depicted in FIG. 1, there may be any number oftransmission systems 102 and any number of radio transmitters 104.

FIG. 2 is a block diagram of an exemplary scheduler 114 in an exemplaryembodiment. The scheduler 114 includes a timeslot division module 202, atimeslot allocation module 204, and an optional timeslot organizationmodule 206. A module may be hardware, software, or a combination ofhardware and software.

In various embodiments, a common timeline is defined between thetransmission system 102 and the radio receiver 106. The timeslotdivision module 202 may partition the timeline into a sequence oftimeslots. The timeslot division module 202 then assigns a positionidentification index to each timeslot. In one example, the positionidentification index is unique and may be identified by both thetransmission system 102 and the radio receiver 106.

In various embodiments, the timeslot division module 202 defines thetimeline by coarse time intervals which are then further divided intotimeslots. In one example, the coarse time intervals may be set by anAbsolute Layer 1 Frame Number (ALFN). The timeslots may be aligned toOFDM symbol numbers that carry data in the physical layer (L1)transmission frame. The L1-transmission frame has 512 OFDM symbols inthe FM mode and 256 OFDM symbols in the AM mode. Any timeslot canthereby be identified by both the radio receiver 106 and thetransmission system 102 by using a 41 bit timestamp comprising a 32 bitcount that identifies the ALFN of the L1 transmission frame and anadditional 9 bit count that identifies the (OFDM Symbol) timeslot numberwithin the L1 transmission frame. The 9 bit count is in a range of 0 to511 in the FM mode and in a range of 0 to 255 in the AM mode. Those ofordinary skill in the art will realize that there are many ways todefine the common timeline and timeslots without departing from thescope and spirit of the exemplary embodiments disclosed herein.

The transmission system 102 may provide sufficient information in thetransmission standard for both the transmission system 102 and a radioreceiver 106 to establish the common timeline. In one example, the ALFNis transmitted in each L1 transmission frame as a part of the StationInformation Service (SIS) messages. The exemplary radio receiver 106 canthen decode the SIS messages, thereby getting the 32 bit value of theALFN belonging to the current received L1 transmission frame. Toidentify the timeslot number within the L1 transmission frame, the radioreceiver 106 may set a count at the first OFDM symbol of the L1transmission frame, and increment this count for every received OFDMsymbol until the end of the L1 transmission frame.

The timeslot allocation module 204 allocates to each service a set ofone or more continuous timeslots carrying information bits belonging tothe service. A continuous set of one or more timeslots that areallocated to a particular service is defined as a grant.

In various embodiments, the scheduler 114 attempts to maximize the sizeof a grant while maximizing the gaps between grants. The scheduler 114may also guarantee a required bandwidth for a service and a maximumallowed latency between grants. The bandwidth and maximum latencyrequired for the different services may be dependant on service type andmay vary between different audio services and data services. Thebandwidth and maximum latency can be parameters associated with eachservice that an operator of the transmission system provides in order toguarantee an expected quality of particular services. The optionaltimeslot organization module 206 creates a gap of timeslots notallocated to the service.

The scheduler 114 may also schedule a periodic grant for fixed bandwidthservices such that a service will receive a fixed size grant ofXgrant_size timeslots, once every fixed interval of Xgrant_interval. Insome embodiments, the scheduler 114 attempts to make the Xgrant_intervalas large as possible without violating the maximum latency requirementfor the related service The scheduler 114 may increase the size of eachgrant (Xgrant_size) to carry more information bits, and then space thegrants in time. For example, if a total bandwidth of a logical channelis 25 Kbps and the bandwidth of a specific data service (denoted DS0) isa continuous 1 Kbps and the maximum allowed latency is equal to aduration of 25 L1 transmission frames, the scheduler 114 may allocateXgrant_size=one L1 transmission frame and Xgrant_interval=25 L1transmission frames. As a result, a transmission allocation (beforeinterleaving) may comprise one L1 transmission frame carrying databelonging to DS0, followed by 24 L1 transmission frames that do notcarry data belonging to DS0, and so forth.

The scheduler 114 may grant timeslots to services before thetransmission of the information bits that are carried in the grant. Invarious embodiments, for fixed bandwidth services, the scheduler 114 canallocate a periodic grant that will be available for service informationbit transmission at any time in the future, until the service isstopped, or until the bandwidth for the service is changed.

In some embodiments, the scheduler 114 provides immediate grants oftimeslots to services very close to the actual time of transmission. Inone example, these grant timeslots accommodate services that are notperiodic. Further, the grant timeslots may accommodate services thathave varying bandwidth and require very short latency between the timethe information is provided to the transmission system 102 until theinformation is transmitted.

The timeslot allocation module 204 may inform the radio receiver 106about the grant allocations for different services. In variousembodiments, the timeslot allocation module 204 inserts a grantallocation message (GAM) into a stream to be transmitted. The GAM mayprovide descriptions of the grant allocations to the different servicesas well as the location of the grants on the common timeline. In oneexample, a GAM can describe a periodic grant to a single service. Inanother example, the GAM can describe multiple periodic grants tomultiple services. The GAM may carry the following information:

-   -   1) Service identification    -   2) ALFN of first grant belonging to the service    -   3) Periodicity of grant in L1 transmission frames    -   4) Index of timeslot or OFDM symbol within the L1 transmission        frame of grant start    -   5) Length of the grant in timeslots    -   6) ALFN of last grant belonging to the service (may not        applicable for a continuous service)

The service identification for audio may use a program number, rangingfrom 0 to 7. The service identification for data services may also use aport number.

The GAM may indicate allocation for services. Further, the GAM maycomprise a single grant, multiple grants, or continuous periodic grants.For example, the GAM can set last_grant_ALFN=first_grant_ALFN.Therefore, validity of the GAM is for only one L1 transmission frame.The GAM may use a special value for a last grant ALFN to indicatecontinuous periodic grants to a service (e.g.,Last_grant_ALFN=0xFFFFFFFF). Further, the GAM can be sent periodicallybut very infrequently, such that radio receivers may have multipleopportunities to receive the GAM information.

In various embodiments, the GAM can be carried as ADS packets. In such acase, the GAM may have a unique port number. In one example, the GAM,itself, may be carried as part of the ADS packet payload.

In another exemplary embodiment, the GAM can be carried as part of aPIDS logical channel as a new type of SIS PDU. For example, the SIS PDUcarrying GAM may use a type field=1 to identify the PDU as a GAM. Insome embodiments, several SIS PDU may be concatenated to carry a singleGAM message.

FIG. 3 depicts a sequence of grant scheduling events on a timeline 302in an exemplary embodiment. The timeline 302 includes L1 transmissionframes 304 which each comprise an ALFN and timeslots 306 aligned to OFDMsymbols. The L1 transmission frames 304 also include a count rangingfrom 0 to 511. In various embodiments, the timeslots 306 are uniquelyidentified by a set of 2 values including the ALFN as well as OFDM countwhich may be denoted as timeslot(ALFN,OFDM_count).

In various embodiments, the scheduler 114 may receive a request toschedule a new data service denoted as DS1 to a logical channel. Thescheduler 114 may also receive the bandwidth and maximum latency for theDS1 service. The maximum latency can be defined in L1 transmissionframes 304 and the bandwidth can be expressed in units of timeslots/perframe. In the present example, the maximum latency is 2 L1 transmissionframes and the bandwidth is m timeslots/frame. The scheduler 114 maythen allocate a periodic grant for DS1 information with a period of 2 L1transmission frames, not exceeding the maximum latency. Each grant isset to a size of t=2*m timeslots, starting from timeslot index r withinthe frame, up to timeslot index r+t−1. The scheduler 114 may then send aGAM at timeslot(n,j), to inform radio receiver 106 of the location andperiod of the DS1 grants. The scheduler 114 may insert additional GAMsperiodically, to inform radio receiver(s) which have not received thefirst GAM.

Those of ordinary skill in the art will realize that there are many waysto implement scheduler functionality, scheduling methods, and GAMprotocols without departing from the scope and spirit of the inventiveconcepts disclosed herein.

In one exemplary embodiment, the grant allocation for all services is apart of NRSC-5 and NRSC-5A layer2 multiplexing. The grant allocationdescribed herein may apply to all main program service (MPS) andsupplemental program service (SPS) fixed data and opportunistic dataprovided by the layer2 multiples, or may apply only to a subset of thestreams multiplexed by the layer2. For example, a particular layer2multiplex may carry MPS, SPS, and fixed data. The scheduler 114 may onlyaddress grant allocation for some services in the fixed data transportstream. In these cases, the GAM may only be sent for the fixed dataservices that are scheduled by the scheduler module.

Further, the multiplexed data from layer2 may go to NRSC-5 (or NRSC-5A)layer1 processing. As a result, the scheduled data as well as all othertransmitted data may go through layer1 scrambling, interleaving channelcoding, and modulation. After time interleaving at the transmitter,consecutive bits of each timeslot 306 will be spread and transmittedover multiple OFDM symbols. The formula by which each data bit isinterleaved in layer1 is well known in the art and may depend on thetype of logical channel that carries the information bit.

FIG. 4 is a flowchart regarding transmitting a GAM in an exemplaryembodiment. In step 402, the timeslot division module 202 divides astream of data into a plurality of timeslots. The stream of data maycomprise one or more audio streams as well as other data streams asdiscussed herein. In one example, the stream of data includes a primaryaudio stream and a secondary stream. The primary audio stream maytransmit a duplication of the primary audio stream over an analogsignal. The secondary stream may comprise digital data including, butnot limited to, traffic reports, weather, and/or data regarding theprimary audio stream.

In step 404, the timeslot allocation module 204 allocates a firsttimeslot of the plurality of timeslots to a first service to form agrant. The timeslot allocation module 204 may also allocate a secondtimeslot to a second service. Those skilled in the art will appreciatethat the timeslot allocation module 204 may allocate any number oftimeslots to any service.

In step 406, the timeslot allocation module 204 generates the GAM thatdescribes the grant and indicates a location of the first timeslot. Invarious embodiments, the grant allocation message describes one or moregrants and indicates one or more locations of one or more timeslots. TheGAM may be encoded by OFDM or COFDM.

In steps 408 and 410, a transmitter transmits the GAM and the pluralityof timeslots to a receiver. In various embodiments, the transmitter andthe receiver are compatible NRSC-5 and NRSC-5A devices.

FIG. 5 depicts the current NRSC-5A transmission standard provision forscheduling multiple audio services in a single P1 logical channel in theprior art. FIG. 5 shows an example of the current allocation of twoaudio services and one data service in P1 logical channel. The servicesare denoted as Prog 0 (corresponding to the MPS audio program 0), Prog 1(corresponding to the SPS audio program 1), and ADS data (correspondingto ADS data service). The layer2 multiplex will assign the servicessequentially in the P1 frame, first to Prog 0, then Prog 1, then ADS.The same allocation will be repeated in subsequent L1 transmissionframes. With this layer2 service multiplexing, information of eachservice is sent over each of the L1 transmission frames.

FIG. 6 shows improved scheduling in accordance with an exemplaryembodiment. The scheduler 114 may first establish a period for theservice scheduling. In this example, the period is 2 L1 transmissionframes. The scheduler 114 may then allocate one large grant for each ofthe services in the period, and repeat that grant in the followingperiod. In the example shown in FIG. 6, Prog 0 is allocated with a grantof size 512 timeslots (a full frame) starting at frame ALFN=K timeslot0. Prog 1 is allocated with a grant of size 508 timeslots starting atframe ALFN=K+1 timeslot 0. The ADS data service is allocated a grant ofsize 4 timeslots starting at frame ALFN=K+1 timeslot 508. The schedulermodule may repeat these grants at a period of 2 L1 transmission frames.Therefore, every frame with ALFN=K+2*n where n=0, 1, . . . is an integerhaving the same allocation as frame ALFN=K. Similarly, every frame withALFN=K+2*n+1 will have the same allocation as frame ALFN=K+1. The sameperiodic grants can continue until one of the services is dropped,added, or have a change in bit rate. In this scheduling embodiment,information belonging to Prog 0 is carried over every other L1transmission frame, with ALFN=K+2*n. Information belonging to Prog 1 orthe ADS data carries over every other L1 transmission frame, withALFN=K+2*n+1.

FIG. 7 is a block diagram of L1 transmission frames wherein two audioprograms are transmitted in subsequent L1 transmission frames in anexemplary embodiment. In various embodiments, every other L1transmission frame contains a multicast program HD1 or HD2. For example,64 packets of MPS may be transmitted in the first L1 transmission frame.Subsequently 64 packets of SPS may be transmitted in the second L1transmission frame. The odd transmission frames (e.g., the third, fifth,seventh, and so on) may transmit packets of HD1 while the eventransmission frames (e.g., fourth, sixth, eighth, and so on) maytransmit packets of HD2. In some embodiments, the presence or absence ofMPS or SPS may be indicated by L2 PCI bits. The transmission schedulemay be broadcast as an ADS packet or by a header extension field in theMPS header or as a new SIS message.

As a result of the transmission of L1 transmission frames in thismanner, the radio receiver 106 that receives the L1 transmission framesmay selectively deactivate unused components (such as a deinterleaver)thereby saving power. Deactivation of unused components of the radioreceiver 106 is further discussed herein. In one example, when the L1transmission frames are transmitted as depicted in FIG. 7, then theradio receiver 106 may achieve 50% or less power savings.

FIG. 8 is another block diagram of L1 transmission frames wherein twoaudio programs are transmitted in subsequent L1 transmission frames inan exemplary embodiment. In various embodiments, every other L1transmission frame contains the Main Program Stream. Unlike the formatof the L1 transmission frames discussed in FIG. 7, however, the secondaudio program (SPS) is transmitted as ADS packets. In one example, 64packets of MPS are transmitted in the first L1 transmission frame. Thisframe's PCI bits are set to indicate the presence of an MPS/SPS but nofixed data. For the second L1 transmission frame, as well as other L1transmission frames of SPS transmitted as ADS packets, the PCI bitsindicate that the frame contains fixed data but not MPS or SPS. The HDCencoder at the transmitter may be configured such that the 64 compressedpackets corresponding to an MPS stream are rate shaped to fit an L1transmission frame. This sort of rate shaping has been applied to otherAudio/Video compression standards. The SPS may not have the same timingalignment requirement that is required of the MPS due to blendingconsiderations. In various embodiments, the same rate shaping may beperformed on the SPS to reduce the buffer requirements on the receiver.

As a result of the transmission of L1 transmission frames in thismanner, the radio receiver 106 that receives the L1 transmission framesmay selectively deactivate unused components (such as the deinterleaver)thereby saving power. In one example, when the L1 transmission framesare transmitted as depicted in FIG. 8, then the radio receiver 106 mayachieve 50% or less power savings. Existing receivers can still receiveMPS. Further, existing receivers may be able to receive SPS encapsulatedin ADS after a software upgrade.

FIG. 9 is a block diagram of multiple logical channels in an exemplaryembodiment. A limitation of the previous allocation of bandwidth betweenMPS and SPS may limit the number of multicast streams to two withoutdegrading the audio quality. One approach to solve this problem would beto use the multi-stream capability of the HDC. The MPS can be split to acore and enhanced stream. The core stream may be transmitted in L1transmission frames of logical channel P1. The remaining bandwidth ofthe L1 transmission frames of the logical channel P1 may be used totransmit SPS streams (e.g., HD2 and HD3) as ADS packets. The enhancedstream of the MPS is transmitted in logical channel P3 (ExtendedHybrid). This approach allows for three or more multicast streams. Itmay not be possible to turn off the receiver when the user is listeningto the MPS but the SPS streams can be time divisioned to turn offinactive symbols thereby saving power.

In one example, 24 Kbps of the core of HD1 (MPS) is transmitted in L1transmission frames of the logical channel P1. 36 Kbps of HD2 (SPS) andHD3 (SPS) are also transmitted as ADS packets in L1 transmission framesof the logical channel P1. Further, in logical channel P3, 24 Kbpsenhanced stream of the MPS is also transmitted. As a result, in someembodiments, the radio receiver 106 may achieve significant powersavings by deactivating radio receiver components when unneeded.

In another example, 32 Kbps of the core of MPS is transmitted in L1transmission frames of the logical channel P1 as an ADS packet. Theremaining 64 Kbps is split to HD2 and HD3 which are also transmitted asADS packets in L1 transmission frames of the logical channel P1. As aresult, in some embodiments, the radio receiver 106 may achieve 50%power savings or less by deactivating radio receiver components whenunneeded. Here, the MPS and SPS may both be time divisioned.

In various embodiments, in order for the radio receiver 106 to receiveand decode audio data within the MPS, SPS, and ADS streams, the radioreceiver 106 is configured to receive and process a message (e.g., GAM)describing the scheduling of these streams. Those skilled in the artwill appreciate that there may be many ways to convey or otherwiseindicate a transmission schedule to a radio receiver 106. The radioreceiver 106 may use this transmission schedule to decode the audio datafrom within the ADS streams.

In other embodiments, the entire bandwidth of the logical channel P1transmits audio streams encapsulated as ADS packets. In one example,when HD1 and HD2 are transmitted at 48 Kbps as ADS packets, the radioreceiver 106 may achieve 50% power savings or less. In another example,when HD1, HD2, and HD3 are transmitted at 32 Kbps as ADS packets, theradio receiver 106 may achieve 66% power savings or less by deactivatingradio receiver components when unneeded. Those skilled in the art willappreciate that the radio receiver 106 may need to be configured toprocess the audio streams contained within the ADS packets. For example,a message (e.g., GAM) describing the scheduling of the ADS streams maybe sent from the radio transmitter 104 to the radio receiver 106 toconfigure the radio receiver 106.

FIG. 10 is another block diagram of multiple logical channels in anexemplary embodiment. In various embodiments, the logical channel P1(main channel) is virtually concatenated with the logical channel P3(extended hybrid). The number of frequency partitions in the extendedhybrid may determine bandwidth in the logical channel P3, and, hence,the bandwidth of the virtual channel. In various embodiments, thelogical channel P1 may use the same or a different channel coding anddeinterleaver than that used for logical channel P3. The selection ofthe deinterleaver scheme for logical channels P1 and P3 may determinethe receiver (e.g., of the radio receiver 106) on/off times.

The radio receiver 106 may achieve different power savings depending onthe frequency partitions. In one example, as depicted in FIG. 10, thelogical channel P1 includes repeating sets of three L1 transmissionframes. The first and second L1 transmission frames include HD2 as ADSpackets as well as 48 Kbps of HD1 (SPS). The third L1 transmission frameincludes data within the ADS packet as well as 48 Kbps of HD1. Thelogical channel P3 also includes repeating sets of three L1 transmissionframes. The first L1 transmission frame includes HD2 as ADS packets. Thesecond L1 transmission frame includes HD3 as ADS packets. The third L1transmission frame includes data as ADS packets. As a result of thispartitioning, the radio receiver 106 may achieve power savings of 33% orless. The convolutional deinterleaver used in logical channel P3currently specified in the NRSC-5A standard reference documents may needto change to accomplish this.

In another example, the logical channel P1 includes repeating sets oftwo L1 transmission frames. The first transmission frame includes HD2 asADS packets as well as 48 Kbps of HD1. The second transmission frameincludes HD3 as ADS packets as well as 48 Kbps of HD1. The logicalchannel P3 also includes repeating sets of two L1 transmission frames.The first L1 transmission frame includes HD2 as ADS packets. The secondL1 transmission frame includes HD3 as ADS packets. As a result of thispartitioning, the radio receiver 106 may achieve power savings of 50% orless.

Further, in another example, the logical channel P1 includes repeatingsets of five L1 transmission frames. The four transmission framesinclude HD2 as ADS packets as well as 48 Kbps of HD1. The fifthtransmission frame includes HD1. The logical channel P3 also includesrepeating sets of five L1 transmission frames. The four L1 transmissionframe includes HD2 as ADS packets. The fifth L1 transmission frameincludes data. As a result of this partitioning, the radio receiver 106may achieve power savings of 20% or less.

FIG. 11 is a block diagram of a radio receiver 106 in an exemplaryembodiment. In various embodiments, the radio receiver 106 is capable ofreceiving and decoding grant allocation messages from the radiotransmitter 104. The decoded grant allocation messages may be used toidentify OFDM symbols that carry information belonging to services thatare used by the radio receiver 106. As a result, the radio receiver 106may deactivate (e.g., turn off) components during OFDM symbols that donot carry information belonging to services in use by the radio receiver106 thereby reducing power consumption.

The radio receiver 106 comprises a tuner 1102, two analog to digitalconverters (ADCs) 1104 and 1106, and digital signal processing hardware(DSPHW) 1108. The tuner 1102 is configured to tune to a desiredcommunication channel transmitted over a specific radio frequency (RF)band, and down-convert it to some intermediate frequency (IF) or to zerofrequency (DC). The down-converted signal can then be sampled by theADCs 1104 and 1106 to form digital representations of the down-convertedsignal. Although two ADCs 1104 and 1106 are depicted in FIG. 11, thoseskilled in the art will appreciate that there may be one or more ADCs.

The DSPHW 1108 may be implemented with digital logic circuitry in orderto demodulate the sampled signal and recover the information that wasmodulated in the transmitted signal. The DSPHW 1108 can include a hardwired digital logic, hard programmable digital logic, a programmableprocessor, or any combination of these.

In various embodiments, the radio receiver 106 may also be configured toinclude a control line between the DSPHW 1108 and the ADC 1106, andanother control line between the DSPHW 1108 and the tuner 1102. TheDSPHW 1108 is capable of controlling the tuner 1102 and the ADC 1106 fortuning and sampling the desired channel. The DSPHW 1108 is also capableof controlling the power consumption of a tuner 1102 by controlling thepower consumption of one or more of the components inside the tuner1102.

In some embodiments, the DSPHW 1108 can completely turn off (i.e.,deactivate) the current consumption of some of the components of thetuner 1102. In one example, the DSPHW 1108 sets one or more tuner 1102components to a power off mode. The DSPHW 1108 may also reduce the powerconsumption of some of the tuner components, but not completelyeliminate the currents to these components, setting them into powerstandby mode. Similarly, the DSPHW 1108 can control the powerconsumption of the ADC 1106, by setting the ADC 1106 to power off orstandby mode. The DSPHW 1108 is also capable of controlling the powerconsumption of the DSPHW 1108 itself, by clock gating clocks into someof the digital circuits of the DSPHW 1108.

Although FIG. 11 depicts a single control line between the DSPHW 1108and the ADC 1106, in various embodiments the radio receiver 106 may beconfigured such that there are any number of control lines between theDSPHW 1108 and the ADCs. For example, the radio receiver 106 may includea control line between the DSPHW 1108 and the ADC 1104 as well asbetween the DSPHW 1108 and the ADC 1106. As a result, the DSPHW 1108 mayindependently control power consumption in each ADC. In otherembodiments, there may be no control line(s) between the DSPHW 1108 andany of the ADCs.

FIG. 12 is a block diagram of an exemplary tuner 1102 with a directconversion architecture in an exemplary embodiment. The tuner 1102comprises components including a low noise amplifier (LNA) 1202, mixers(MIX) 1204 and 1206, shifter 1208, local oscillator buffer (LOB) 1210,low pass filters (LPFs) 1212 and 1214, automatic gain controls (AGCs)1216 and 1218, a voltage controlled oscillator (VCO) 1220, a phase lockloop (PLL) 1222, and a power control 1224.

In various embodiments, a radio frequency signal is received by theantenna of the radio receiver 106. The signal is first amplified by theLNA 1202. The signal is then split into two branches, including aninphase branch and a quadrature phase branch. The signal in the inphasebranch may be mixed in MIX 1204 with a sinusoid, and the signal on thequadrature branch may be mixed in MIX 1206 with a sinusoid shifted by 90degrees (via shifter 1208) to produce a replica of the signal centeredon a low intermediate frequency (IF) or centered on zero frequency (DC).The down-converted signals are then passed through LPFs 1212 and 1214,respectively, which reject signals that are outside the band of thesignal of interest. ACGs' 1216 and 1218 circuitry may adjust the powerof the filtered signals to a desired level. The outputs of the AGCs 1216and 1218 are sent to the ADCs 504 and 506, respectively, for sampling.

Optionally, the sinusoidal signal received by the MIXs 1204 and 1206 maybe initially generated by the PLL 1222. In one example, the PLL 1222generates a signal and provides the signal to a voltage controlledoscillator (VCO) 1220 which then provides the signal to a localoscillator buffer (LOB) 1210. The resulting sinusoidal signal is thensplit. The MIX 1204 subsequently receives the sinusoidal signal. Ashifter 1208 shifts the split sinusoidal signal by ninety degrees, andthen provides the shifted sinusoidal signal to the MIX 1206. Thoseskilled in the art will appreciate that there are many ways to generatea sinusoidal signal.

The radio receiver 106 may also implement power control circuitry thatcan reduce the power consumption of some or all of the components in thetuner 1102. In some embodiments, the currents received by one or morecomponents can be turned off, thereby setting the component(s) to poweroff mode, or, alternately, the currents can be reduced, thereby settingthe component(s) into power standby mode. The power control circuitrymay be controlled by the DSPHW 1108 using one or more control linesleading to power control 1224.

In some embodiments, the current to the tuner 1102 can be significantlyreduced by setting components to power off or standby mode while stillmaintaining the phase of a local oscillator carrier generated by the PLL1222. Those skilled in the art will appreciate that there may be manymethods for power control in the tuner 1102 using embodiments describedherein. Further, it should be understood by one skilled in the art thatvarious embodiments described herein can be used in any other tunerarchitecture, such as dual conversion or super heterodyne.

In various embodiments, the radio receiver 106 is capable ofsynchronizing to a common timeline established with the transmissionsystem 102, where the common timeline is partitioned into a sequence oftimeslots. The radio receiver 106 may be capable of determining a starttime of each timeslot as it is received.

As discussed herein, the common timeline may be defined by coarse timeintervals, which are then further divided into fine timeslots. Thecoarse time intervals may be set by the ALFN and the fine timeslots maybe aligned to the OFDM symbol numbers that carry the data in the L1transmission frame. During the channel synchronization process, theDSPHW 1108 may synchronize to the L1 transmission frame boundary (e.g.,by synchronizing to a system control channel (SCCH)). The DSPHW 1108 maykeep a fine timeslot counter that is set to 0 on the first OFDM symbolin the L1 transmission frame, and which may be incremented by one afteran interval of OFDM symbol duration. The counter may be reset to 0 atthe start of each L1 transmission frame. The radio receiver 106 may alsoparse station information service (SIS) packets to extract the ALFNnumber of the received L1 transmission frame. The combination of ALFNnumber and the fine interval count within each L1 transmission frame mayuniquely identify each timeslot interval on the common timeline.

In various embodiments, the radio receiver 106 is also capable ofreceiving, decoding, and parsing GAM sent from the transmission system102. In one example, a GAM is transmitted on a PIDS channel as asequence of SIS messages. The radio receiver 106 may decode the SISmessages in each logical channel to retrieve the GAM body.

In another example, the GAM is transmitted on a dedicated port on an ADSdata stream. In this example, the radio receiver 106 may demodulate theL1 transmission frames, extract the ADS packets, and then parse thepackets having a port number associated with the GAM to retrieve the GAMbody.

After retrieving the GAM, the radio receiver 106 may check a service IDfield in the GAM to identify GAMs that describe grant allocations forservices that are being used by the radio receiver 106 or by any otherdevice coupled to the radio receiver 106 that receives data from theradio receiver 106. The radio receiver 106 may then retrieve the grantallocation information, thereby identifying which timeslots belonging todifferent services including those that may be in use by the radioreceiver 106.

After identifying the allocated timeslots from the GAM, the DSPHW 1108may calculate which OFDM symbols are needed to be received anddemodulated in order to retrieve the information that belongs to theservices used by the radio receiver 106. The required OFDM symbols maybe denoted as active symbols. The OFDM that are not active symbols aredenoted as inactive symbols.

To calculate the active symbols, the DSPHW 1108 may take intoconsideration the time interleaving that is performed at thetransmission system 102. The interleaving operation of the transmissionspreads the information of each timeslot at the input of layer1 into aplurality of transmitted OFDM symbols. The DSPHW 1108 may map thegranted timeslots into an equal or greater number of active OFDM symbolsthat are carrying information belonging to the services in use.

The mapping of granted timeslots to active symbols calculation maydepend on a type of interleaver used by Layer 1. Each interleaver mayrequire a different type of mapping function in the DSPHW 1108.

FIG. 13 shows mapping grants into active symbols in an FM logicalchannel that is interleaved using interleaver I with latency of M OFDMsymbols in an exemplary embodiment. In such a logical channel, theactive symbols are all the OFDM symbols belonging to any usedinterleaver block, where a used interleaver block is comprised of M OFDMsymbols that are interleaved together and carry one or more timeslotsbelonging to a service in use. As shown, the modulation profile is MP1,MP2, or MP3 and the logical channel is P1. The interleaver latency isM=512 OFDM symbols, aligned to an L1 transmission frame. An L1transmission frame with ALFN=K has a grant of t timeslots, from timeslotr until timeslot r+t−1, (highlighted with gray shading). The activesymbols are an entire P1 frame corresponding with ALFN=K, composed of512 OFDM symbols. In L1 transmission frame numbered ALFN=K+1 there areno granted timeslots, therefore the entire P1 frame of 512 OFDM symbolsare inactive symbols.

FIG. 14 shows mapping grants into active symbols in an FM logicalchannel that is interleaved using interleaver IV with latency of K OFDMsymbols in an exemplary embodiment. In such a logical channel, theactive symbols are all the OFDM symbols aligned with the grant timeslotsthemselves followed by additional K OFDM symbols. As shown, a modulationprofile can be MP2, MP3 and the logical channel may be P3. Theinterleaver latency is K=1024 OFDM symbols. FIG. 14 shows a grant of jtimeslots, from timeslot r until timeslot r+j−1 in L1 transmission frameALFN=K, (highlighted with gray shading). The active symbols are rangingfrom timeslot r in L1 transmission frame ALFN=K until timeslot r+j−1 inALFN=K+2.

After determining which of the received OFDM symbols are active orinactive, the DSPHW 1108 may send power control signals to one or morecomponents of the tuner 1102, the ADC 1104, ADC 1106, and/or digitalhardware components. During the active symbols, the control signals mayset the different components into power on mode, thereby allowing thereceiving and demodulating of active symbols and extracting theinformation bits belonging to a service in use. During the inactivesymbols, the control signals may set the different components into powerdown or standby mode, thereby reducing the power consumption of thereceiver during the inactive symbols.

In various embodiments, some components may be set to power down mode,some components may be set to standby mode, while others may be active.In one example, certain components may be left in the previous state(e.g., in power down mode) if one or more GAMs indicate a service thatis not in use. In another example, the DSPHW 1108 may anticipate aservice that will be active based one or more GAMS. The DSPHW 1108 mayset one or more components to power on mode from power down mode toallow one or more components time to function correctly (e.g., allow thecomponents to “warm up”).

FIG. 15 shows a received transmission partitioned into a sequence ofOFDM symbols (e.g., numbered 0 to 511) in L1 transmission frames in anexemplary embodiment. In various embodiments, the radio receiver 106 isinformed by a GAM that a service in use is allocated in periodic grantof t timeslots, from timeslot r until timeslot r+t−1, where thetimeslots are aligned to OFDM symbols. The DSPHW 1108 may then identifythe active symbols for receiving the service in use. In this example,the active symbols are all the OFDM symbols belonging to L1 transmissionframes that carry the grant timeslots before the Layer 1 interleavingoperation.

The DSPHW 1108 may then send one or more control signals to one or morecomponents of the tuner 1102, the ADC 1104, ADC 1106, and/or digitalhardware components, turning them on (i.e., activating the components)for the duration of the active symbols, and turning them to power downor standby mode for the duration of the inactive symbols. Therefore, thepower consumption of the radio receiver 106 component(s) may be reducedduring the inactive symbols. The average power consumption of thereceiver may, therefore, also be reduced.

In various embodiments, the radio receiver 106 may tune and demodulate asecondary channel during an interval of consecutive inactive timeslots.The secondary channel may be transmitted over a different frequency thanthe primary channel. The secondary channel may also carry a differentkind of communication signal than the primary channel.

During an interval of inactive timeslots, the DSPHW 1108 may configurethe tuner 1102 to tune to the secondary channel carrier frequency. TheDSPHW 1108 may then demodulate and decode the digital data transmittedover the secondary channel, until the end of the inactive timeslotsinterval, or until sufficient data is collected from the secondarychannel.

In some embodiments, the primary channel is a hybrid FM signal and thesecondary channel is another hybrid FM on a different carrier frequency.In other embodiments, the primary channel is a hybrid FM signal and thesecondary channel is an analog FM signal, carrying a DirectBand digitalsignal. Any combination of primary and secondary channel types may beutilized in embodiments discussed herein.

FIG. 16 is a flowchart regarding receiving the grant allocation messagein an exemplary embodiment. In step 1602, the radio receiver 106receives a grant allocation message describing a first service and alocation of a timeslot from a transmitter such as a radio transmitter104. In step 1604, the radio receiver 106 decodes the GAM to identifyOFDM symbols that carry service information (i.e., information regardingone or more services). The radio receiver 106 may also parse, format, orunformat the GAM to retrieve desired information.

In step 1606, the radio receiver 106 receives a plurality of timeslots,including the timeslot referred to within the GAM. After processing oneor more of the plurality of timeslots, the radio receiver 106 sets apower mode for receiver components. In one example, the radio receiver106 sets one or more components of the tuner to power down or standbymode. The radio receiver 106 may also set one or more other componentsto power on mode (i.e., activate). Those components that are active maybe necessary for the radio receiver 106 to perform desired servicesassociated with one or more timeslots within the plurality of timeslots.Similarly, those components that are in power down or standby mode maynot be used within one or more timeslots within the plurality oftimeslots.

The above-described functions and components can be comprised ofinstructions that are stored on a computer readable storage medium. Theinstructions can be retrieved and executed by a processor. Some examplesof instructions are software, program code, and firmware. Some examplesof computer readable storage medium are memory devices, tape, disks,integrated circuits, and servers. The instructions are operational whenexecuted by the processor to direct the processor to operate in accordwith embodiments of the present invention. Those skilled in the art arefamiliar with instructions, processor(s), and computer readable storagemedium.

The present invention has been described above with reference toexemplary embodiments. It will be apparent to those skilled in the artthat various modifications may be made and other embodiments may be usedwithout departing from the broader scope of the invention. Therefore,these and other variations upon the exemplary embodiments are intendedto be covered by the present invention.

1. A radio receiver, the radio receiver comprising: a tuner; and digitalsignal processing hardware (DSPHW) communicatively coupled with thetuner, the DSPHW configured to: configure the tuner to tune to a primarycarrier frequency, configure the tuner to tune to a secondary carrierfrequency during an interval of consecutive inactive timeslots on aprimary channel associated with the primary carrier frequency, anddemodulate and decode digital data transmitted over a secondary channelassociated with the secondary carrier frequency.
 2. The radio receiverof claim 1, wherein the primary carrier frequency and the secondarycarrier frequency are in a predetermined radio frequency band.
 3. Theradio receiver of claim 1, wherein the primary carrier frequency and thesecondary carrier frequency are different frequencies.
 4. The radioreceiver of claim 3, wherein the secondary channel carries a differentkind of communication signal than the primary channel.
 5. The radioreceiver of claim 3, wherein the primary channel is a first hybrid FMsignal and the secondary channel is a second hybrid FM signal.
 6. Theradio receiver of claim 3, wherein the primary channel is a hybrid FMsignal and the secondary channel is an analog FM signal, the secondarychannel carrying a DirectBand digital signal.
 7. The radio receiver ofclaim 3, wherein the DSPHW is further configured to: configure the tunerto tune to the primary carrier frequency after the interval ofconsecutive inactive timeslots, and configure the tuner to tune to theprimary carrier frequency after an amount of data is collected from thesecondary channel.
 8. The radio receiver of claim 1 further comprising:one or more analog to digital converters (ADC).
 9. A method of operatinga radio receiver, the method comprising: configuring a tuner to tune toa primary carrier frequency; configuring the tuner to tune to asecondary carrier frequency during an interval of consecutive inactivetimeslots on a primary channel associated with the primary carrierfrequency; and demodulating and decoding digital data transmitted over asecondary channel associated with the secondary carrier frequency. 10.The method of claim 9, wherein the primary carrier frequency and thesecondary carrier frequency are different frequencies.
 11. The method ofclaim 10, wherein the secondary channel carries a different kind ofcommunication signal than the primary channel.
 12. The method of claim10, wherein the primary channel is a first hybrid FM signal and thesecondary channel is a second hybrid FM signal.
 13. The method of claim10, wherein the primary channel is a hybrid FM signal and the secondarychannel is an analog FM signal, the secondary channel carrying aDirectBand digital signal.
 14. The method of claim 10 furthercomprising: configuring the tuner to tune to the primary carrierfrequency after the interval of consecutive inactive timeslots; andconfiguring the tuner to tune to the primary carrier frequency after anamount of data is collected from the secondary channel.
 15. Anon-transitory computer-readable storage medium having embodied thereona program, the program being executable by a processor to perform amethod for operating a radio receiver, the method comprising:configuring a tuner to tune to a primary carrier frequency; configuringthe tuner to tune to a secondary carrier frequency during an interval ofconsecutive inactive timeslots on a primary channel associated with theprimary carrier frequency; and demodulating and decoding digital datatransmitted over a secondary channel associated with the secondarycarrier frequency.
 16. The non-transitory computer-readable storagemedium of claim 13, wherein the primary carrier frequency and thesecondary carrier frequency are different frequencies.
 17. Thenon-transitory computer-readable storage medium of claim 14, wherein thesecondary channel carries a different kind of communication signal thanthe primary channel.
 18. The non-transitory computer-readable storagemedium of claim 14, wherein the primary channel is a first hybrid FMsignal and the secondary channel is a second hybrid FM signal.
 19. Thenon-transitory computer-readable storage medium of claim 14, wherein theprimary channel is a hybrid FM signal and the secondary channel is ananalog FM signal, the secondary channel carrying a DirectBand digitalsignal.
 20. The non-transitory computer-readable storage medium of claim14 wherein the method further comprises: configuring the tuner to tuneto the primary carrier frequency after the interval of consecutiveinactive timeslots; and configuring the tuner to tune to the primarycarrier frequency after an amount of data is collected from thesecondary channel.